It is customary in modern practice to use stationary keel blocks to support a vessel on a building berth. The keel blocks are arranged in longitudinal rows and spaced at a certain distance from one another, depending on the load distribution (cf. A. K. Syrkov, Sovremennye sudostroitelnye verfi/Modern Shipyards/, Sudostroyeniye Publishers, Leningrad, 1976).
Each keel block comprises a support and a lifting mechanism installed in the support and bearing a housing which accommodates a support pad (cf. M. K. Glozman et al., Technologichnost konstruktsiy korpusa sudna/Technological Aspects of Hull Designs/, Sudostroyeniye Publishers, Leningrad, 1971). The lifting mechanism may be hydraulic or of any other type.
The known systems for supporting and handling vessels or parts of vessels on a building berth are disadvantageous in that they necessitate the use of hauling carriages or trains composed of such carriages, which are rolled in under the bottom of a vessel resting on keel blocks. The carriages are provided with jacks which lift the vessel from the keel blocks so that she is supported by the carriages and can thus be moved to a desired location.
Independent hauling trains are normally used to transfer a vessel in the longitudinal and transverse directions with respect to the berth axis.
The above-mentioned disadvantage is all the more pronounced in the case of progressive-sectional assembly of hulls which makes it necessary to move hull parts in both the longitudinal and transverse directions; the great number of assembly stations calls for a corresponding number of handling operations and means to carry them out.
For example, when side tank modules have to be moved in a dry dock, it takes two self-propelled trains to haul them in the longitudinal direction and two more trains to carry them in the transverse direction, while in the course of assembly the modules rest on a system of keel blocks.
The provision of separate keel block and hauling carriage systems for supporting and handling a vessel on a building berth requires considerable capital investment.